Gas springs are employed in a variety of applications. Gas springs are used to assist in the opening and holding open of various hinged items such as trunk lids, engine hoods, lift gates, vehicle doors, cabinet doors, and windows. The force exerted by gas springs varies with the temperature of the gas in the spring. Higher temperatures increase gas pressures in the spring requiring higher closing forces while lower temperatures decrease gas pressures and reduce lifting and hold open forces.
Solutions exist in the art that employ secondary gas volumes separated from the primary gas volume by a temperature sensitive check valve. These secondary gas volumes, although effective in compensating for temperature variations of the gas within the gas spring, either increase the diameter or length of the gas spring. Increases in package diameter or length prevent the use of these temperature compensated gas springs, in many applications. A gas spring is needed that provides temperature compensation while maintaining a compact package profile.
FIG. 1 shows a schematic representation of one embodiment of a temperature compensating gas spring 100, in accordance with the prior art. A hollow cylinder 110 is separated into a front chamber 112 and a rear chamber 114 by a temperature compensation module (TCM) 116. A piston assembly 120 includes a solid piston 122 connected to a solid piston rod 124. Hollow cylinder 110 is charged with a pressurized gas 118, such as nitrogen, which pressurizes the front chamber 112 and the rear chamber 114.
TCM 116 operates in response to temperature. At temperatures above a design temperature of the TCM 116, the temperature compensating gas spring 100 operates as if the rear chamber 114 does not exist. When the temperature falls below the design temperature of the TCM 116, a valve 134 on the TCM 116 opens and the operating volume of the gas spring 100 is increased.
Other temperature compensation schemes exist involving various types of valves that control the flow of the gas from one area of the gas spring to another at varying rates. Still others use pumps to regulate the pressure in the gas spring. These solutions require additional components that increase their size, weight and cost. Still other temperature compensation schemes involve multiple gas types within the gas spring increasing the complexity of manufacture and requiring strict separation of the different gases.
It is therefore desirable to provide a temperature compensating gas spring that overcomes the limitations, challenges, and obstacles described above.